Preheat the oven to 200°C. Combine the garlic, rosemary, thyme, mustard, olive oil, salt and pepper in a small bowl.

Score the top side of the lamb with a sharp knife and place in a large roasting dish. Spread the garlic and herb mixture over the lamb, rubbing into the scored cuts. Drizzle with extra olive oil.

Roast in the preheated oven for 1 hour 30 minutes for medium, or until the lamb is cooked to your liking. Baste frequently.

After 50 minutes, add the vegetables, garlic bulb and sprigs of rosemary. Toss to coat in oil. Season with salt and pepper. Cook the vegetables for 40 minutes, or until they are tender and golden.

Meanwhile, prepare the mint sauce. Place the vinegar, caster sugar and water into a small saucepan and stir over low heat until the sugar dissolves. Remove from the heat and allow to cool slightly before stirring in the chopped mint.